What's with the obviously half made up? I thought we weren't supposed to deny canon to suit our needs.
We were not, but thankfully, there is enough evidence in the story.
Seki: "It's just that lately, Senpai... you haven't been replying to me at all..."
Yuu: "Well, uh, it's just... I've been kinda busy lately, you know?"
Seki: "Plus, you haven't asked me on a date... like, at all lately..."
Yuu: "Uh, yeah... but that was because you were the one who asked me out that one time..."
Wait, hold up! So they went on one date that she invited him on, and now she's acting like his girlfriend!?
Like I said, she sorta made up stuff about dates (implying he did invite her before) to invoke pity/sympathy. And from the first excerpt you can see that she was the one messaging him, with him replying at first but then stopping at some point.
There's legit nothing in their interaction pointing towards him disliking Seki as a person
Where did I say he dislikes her as a person? I am saying he is not interested.
I agree he's not romantically interested in her
It's not just lack of romantic interest, he doesn't look that interested in communicating with her at all. And leaving her on read (from this chapter) is just another indicator of that. And no, walking her home isn't interest, because she came uninvited to his house and was being a pain in the ass, all he is doing is showing her the door in a courteous way.
Hikari asks Aya more questions
Look, in one case we have Yami teasing and Yuu getting flustered. In the other case we have Hikari asking endless questions and Yami being passive-agressive (and she is not teasing at all, unlike what you suggest), trying to push her off. Like an enthusiastic dog trying to get an annoyed cat to play with it.
Their intentions are different, their moods are different, their reactions are different, even the side initiating the conversation is different. I get it, since the setting is purposefully the same, you're trying to see their interactions as similar too, but it just doesn't work because they were set up for different purposes.
He literally doesn't ask anything else about her
Except a small detail - her name, which he wouldn't ask if he was disinterested.
She's being kind of a jerk to someone she just met and half of what you read as flustered I read as defensive
He reacted the same way he did when they were in relationship.
And this is less important, but he even mirrors Yami's gesture in their conversation:
Although maybe it's just me.
B/c he's not a jerk and she spent time talking to him and listening.
The important part is that she did cheer him up.
And we're still comparing his conversations with Yami and with Seki, right? Because in the latter all he did was softly trying to push her away, the only emotional reaction being his firm rejection.
Have you never been an ear to an almost stranger when they're sad?
I would never tell a stranger I don't care about any details of my private life.